2 Chronicles 20:20-23

Early the next morning the army of Judah went out into the wilderness of Tekoa. On the way Jehoshaphat stopped and said, “Listen to me, all you people of Judah and Jerusalem! Believe in the LORD your God, and you will be able to stand firm. Believe in his prophets, and you will succeed.” After consulting the people, the king appointed singers to walk ahead of the army, singing to the LORD and praising him for his holy splendor. This is what they sang: “Give thanks to the LORD; his faithful love endures forever!” At the very moment they began to sing and give praise, the LORD caused the armies of Ammon, Moab, and Mount Seir to start fighting among themselves. The armies of Moab and Ammon turned against their allies from Mount Seir and killed every one of them. After they had destroyed the army of Seir, they began attacking each other.